we have two servers one is application and front end server.i installed the workflow manager in app server,i checked the workflow service application proxy in services it is showing Workflow connected.
when i tried to create the 2013 workflow i am not getting the option to select the 2013 workflow and it is showing following message.

The option for the SharePoint 2013 workflow platform is not available because the workflow service is not configured on the server.

In my case, I had used a BLANK site template to create my site. Took a long time to figure out that 2013 workflow was available on every other site in the collection, just not on my SPWeb that I provisioned with the BLANK site template. My guess is some hidden features are stapled to other templates, but not the blank template. I fixed my problem by deleting the SPWeb, creating a team site, deleting all the junk that comes with a team site. 2013 workflow in SPDesigner worked just fine after that.